The application generally relates to load bearing supports. The application relates more specifically to load bearing columns constructed of multiple stacked drums with a resilient core member surrounded by filler material.
Various devices disclosed in the prior art are designed and used to provide support to a mine roof. Underground mining results in removal of material from the interior of a mine, thereby leaving unsupported passageways of various sizes within the mine. The lack of support in such passageways may cause mine roof buckling and/or collapse. Thus, it has been desirable to provide support to mine roofs to prevent, delay, or control collapse thereof.
In both underground mining and areas of seismic activity, supports must be engineered to withstand enormous forces propagating through the earth. Building and bridge structures may include modified foundations designed to isolate the superstructure from major ground motion during an earthquake. Such supports for building structures are intended to avoid the transmission of high seismic forces.
Bridges and building structures which are located in an earthquake zone are capable of being damaged or destroyed by seismic forces. In general bridge structures may be constructed with bearings between the bridge's deck or superstructure and the bridge supporting columns to permit relative movement between the two. It is also known to provide damping for the movement upon these bearings of superstructure relative to supports, however the permitted relative movement is not large and furthermore it is not always preferred to attempt to hold a superstructure in a position around a neutral point with respect to the supports.
In underground mining applications, supports of aerated concrete in a hollow tube have been used to permit a support to yield axially in a controlled manner that prevents sudden collapse of an underground mine roof. Such supports yield axially as the aerated concrete within the product is crushed and maintains support of a load as it yields.
An oak wood post having a length of 6.5 feet and a diameter of 6 inches will have a slenderness (height to width) ratio of 26. Such a post will have a maximum axial load capacity of about 16,000 lbs. For a post formed from spruce, the maximum safe axial load handling capability for a post that is 6.5 feet in length and 6 inches in diameter is about 13,600 pounds. In addition, when a wood post yields by kneeling or buckling, such yielding will result in catastrophic failure of the post in which the post can no longer support the load.
Because of the obvious problem associated with such catastrophic failure of posts, various mine props have been developed in the art for supporting the roof of an underground mine. Such mine props have included, various configurations of wood beams encased in metal housings, and complex hydraulically controlled prop devices. Such props, however, do not allow for controlled axial yielding while preventing sideways buckling or kneeling in a simple, lightweight prop that can be hand carried by a user.
U.S. Pat. No. 5,308,196 to Frederick discloses a prior art mine roof support comprising a container that is placed between the mine roof and the mine floor and filled with a load-bearing material.
In instances where a support is compressed, whether due to seismic forces or geological forces, the support generally is incapable of rebounding when the load is reduced or removed. What is needed is a support that can compress under extreme loads and rebound to maintain contact with the load, and which satisfies one or more of these needs or provides other advantageous features. Other features and advantages will be made apparent from the present specification. The teachings disclosed extend to those embodiments that fall within the scope of the claims, regardless of whether they accomplish one or more of the aforementioned needs.